Fluid based thermal conductivity control

ABSTRACT

A temperature control system may include a compartment having at least one side with low thermal conductivity and a side with a double wall, the double wall having an interior wall and an exterior wall, the interior wall and the exterior wall having high thermal conductivity and forming a channel therebetween and a reservoir connected to the channel. A drive may be contained within the reservoir, wherein the drive is responsive to a temperature within the compartment to transfer a liquid with high thermal conductivity from the reservoir into the channel to increase thermal conductivity between the interior of the compartment and the exterior of the compartment, and allows a gas with low thermal conductivity to be present within the channel when the channel does not contain the liquid to decrease thermal conductivity between the interior of the compartment and the exterior of the compartment.

CROSS-REFERENCE

This application claims priority to U.S. Provisional Application No. 61/883,428, filed on Sep. 27, 2013, and entitled “FLUID BASED THERMAL CONDUCTIVITY CONTROL,” the disclosure of which is incorporated by reference in its entirety.

BACKGROUND

The present invention relates generally to power electronics compartment and, in particular, to a fluid based thermal conductivity control system and method to control the temperature within the power electronics compartment.

Power electronics, such as a battery and/or related circuitry, are utilized to power the electrical components used in various types of vehicles and systems. Many batteries generate non-negligible heat when in operation. This heat may build up around the battery, causing a reduction in efficiency of the battery, damage to the battery, and possibly even failure of the battery. To cool the compartment, systems with tubes throughout the compartment containing pressurized gas or liquid have been utilized. These systems have a large number of moving parts that break down and/or malfunction. Also, batteries generally do not perform well in a low temperature environment, which can be present if the battery begins operation after the battery has been out of operation for an extended period of time. If a battery or other power electronics incurs sudden high power operation in a low temperature environment, degradation and/or damage may result.

SUMMARY

A temperature control system may include a compartment having at least one side with low thermal conductivity and a side with a double wall, the side with the double wall having an interior wall and an exterior wall, the interior wall and the exterior wall having high thermal conductivity and forming a channel therebetween and a reservoir connected to the channel. A drive may be contained within the reservoir, wherein the drive is responsive to a temperature within the compartment to transfer a liquid with high thermal conductivity from the reservoir into the channel to increase thermal conductivity between the interior of the compartment and the exterior of the compartment, and allows a gas with low thermal conductivity to be present within the channel when the channel does not contain the liquid to decrease thermal conductivity between the interior of the compartment and the exterior of the compartment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic of a fluid based thermal conductivity control assembly in a non-conducting mode.

FIG. 1B is a schematic of the assembly of FIG. 1A in a conducting mode.

FIG. 2 is a schematic of the assembly of FIG. 1B showing a snap disk actuator.

FIG. 3 is a schematic of the assembly of FIG. 1B showing a fluid expansion actuator.

FIG. 4 is a schematic of the assembly of FIG. 1B showing a solenoid actuator.

FIG. 5A is a schematic of a fluid based thermal conductivity control assembly showing an alternate embodiment in a non-conducting mode.

FIG. 5B is a schematic of the assembly of FIG. 5A in a conducting mode.

DETAILED DESCRIPTION

FIG. 1A is a schematic of a fluid based thermal conductivity control assembly in a non-conducting mode, while FIG. 1B is a schematic of the assembly of FIG. 1A in a conducting mode. Control assembly 18 includes compartment 20, channel 22, and reservoir 24. Compartment 20 includes sides 26, double wall 28 (which includes exterior wall 28 a and interior wall 28 b), and compartment interior 30. Channel 22 includes gas 32 and fins 34 in the non-conducting mode, and gas 32, fins 34, and liquid 36 in the conducting mode. Reservoir 24 includes liquid 36 and drive 38 in the non-conducting mode, and gas 32, liquid 36, and drive 38 in the conducting mode. Drive 38 includes piston 40 and paraffin pellet 42, which acts as an actuator to move piston 40. Control assembly 18 may also include vent tube 44.

Sides 26 and double wall 28 form compartment 20, which is a container configured to house power electronics (not shown), such as a battery or plurality of batteries, in compartment interior 30. Sides 26 may contain a hatch that opens and allows access to compartment interior 30 and/or may contain apertures that allow wires or other apparatus to communicate with devices within compartment interior 30.

Double wall 28 forms channel 22 between exterior wall 28 a and interior wall 28 b. Channel 22 is connected to reservoir 24, which forms an enclosure in which fluid (gas 32 and/or liquid 36) cannot flow in or out. Channel 22 (and double wall 28) is adjacent to compartment 20 and may form more than one side of compartment 20, depending on the desired thermal conductivity characteristics of control assembly 18. Within channel 22 and attached to double wall 28 may be fins 34 that protrude into channel 22 and provide a larger surface area of double wall 28. Double wall 28 may be made from a material exhibiting high thermal conductivity, such as aluminum, while sides 26 may be made from a material exhibiting low thermal conductivity (thermal insulator).

Reservoir 24 is attached to channel 22 such that gas 32 and/or liquid 36 may flow between channel 22 and reservoir 24. Reservoir 24 may be in contact with compartment 20 such that reservoir 24 and compartment 20 share sides 26 or double wall 28. The volume within reservoir 24 may vary with different embodiments depending on the amount of gas 32 and/or liquid 36 needed. Reservoir 24 may be made from a material exhibiting high thermal conductivity or from a material exhibiting low thermal conductivity, depending on the design and desired thermal conductivity of control assembly 18. Within reservoir 24 (in addition to gas 32 and liquid 36) may be drive 38, which can include piston 40 and paraffin pellet 42. Piston 40 is configured to move within reservoir 24 and provide a barrier between gas 32 and liquid 36. Paraffin pellet 42 may be positioned between double wall 28 of reservoir 24 and piston 40 and attached to one or both (explained in greater detail below) so as to move piston 40 depending on the desired temperature of compartment interior 30 and thermal conductivity characteristics of channel 22.

Gas 32 is a gas exhibiting low thermal conductivity (poor thermal conductor) and may have low reactive properties, such as argon. Gas 32 may also be such substances as air or dry nitrogen. Gas 32 should be a substance that does not react or minimally reacts with liquid 36 and may have a condensation temperature outside the expected operating and storage temperature ranges of control assembly 18.

Liquid 36 may be a liquid exhibiting high thermal conductivity (good thermal conductor). Liquid 36 may be non-hazardous and/or non-toxic and may be such substances as a fluorocarbon-based fluid (such as flourinert), oil, water, refrigerant, ammonia, or a propylene glycol/water mixture. Liquid 36 should be a substance that does not react or minimally reacts with gas 32. Also, liquid 36 should have a freezing and boiling temperature outside the expected operating and storage temperature ranges of control assembly 18. The selection of gas 32 and liquid 36 should be made depending on the reactiveness between the two substances and the desired difference between the thermal conductive mode and the thermal non-conductive mode. For example, using argon as gas 32 and propylene glycol/water as liquid 36 may yield a ratio of heat transfer between the conductive mode and the non-conductive mode of approximately 35:1 (liquid 36 would conduct heat approximately 35 times greater than gas 32).

Fins 34 may be present on double wall 28 within channel 22 to aid in the conduction of heat by providing an increased surface area of double wall 28, allowing more contact between double wall 28 and liquid 36 for heat to be conducted. Fins 34 would not span the full width of channel 22, but rather would protrude from double wall 28 into channel 22. Fins 34 may be made from the same material as double wall 28 or may be constructed from a different material having high or low thermal conductivity. Additionally, the interior surface of double wall 28 may be configured to increase or decrease conductivity by varying the smoothness or roughness of the surface.

Vent tube 44 allows gas 32 to flow between the upper portion of channel 22 and the gas portion of reservoir 24. Vent tube 44 prevents the buildup of pressure of gas 32 in channel 22 when liquid 36 is present within channel 22 and, conversely, prevents the buildup of pressure of gas 32 in reservoir 24 when liquid is present within reservoir 24. While shown in FIGS. 1A and 1B as being within compartment interior 30, vent tube 44 may also be outside compartment interior 30.

In the present embodiment, paraffin pellet 42 acts as an actuator and is a material that exhibits thermal expansion when changing from a solid state to a liquid state due to increase in temperature of the material and exhibits contraction when changing from a liquid state to a solid state due to decrease in temperature. Paraffin, in a pellet form, may be enclosed within a volume in reservoir 24 that is in thermal communication with compartment interior 30. The portion of reservoir 24 in which paraffin pellet 42 is positioned may be made from materials exhibiting high thermal conductivity so as to allow thermal communication between paraffin pellet 42 and compartment interior 30. While the material configured to act as an actuator is discussed as paraffin pellet 42, other suitable materials may be used to move piston 40.

Piston 40 is adjacent or connected to paraffin pellet 42 such that the increase in volume of paraffin pellet 42 caused by a state change of paraffin pellet 42 from solid to liquid due to change in temperature causes piston 40 to move. As seen in FIG. 1B, which shows control assembly 18 in the conducting mode, paraffin pellet 42 moves piston 40 within reservoir 24, causing reservoir 24 to have less volume available for liquid 36 and more volume available for gas 32. This causes liquid 36 to flow into channel 22, making channel 22, along with double wall 28, more thermally conductive than if gas 32 where present within channel 22. The presence of liquid 36 within channel 22 allows heat to leave compartment interior 30 through double wall 28, channel 22, and liquid 36, which acts as a thermally conductive bridge to reduce the temperature of compartment interior 30 and the components within compartment 20. Heat may travel from compartment interior 30 through double wall 28, channel 22, and liquid 36 to ambient air or a heat sink adjacent to double wall 28 opposite compartment 20.

The reduction of the temperature in compartment interior 30 is important, for compartment 20 may contain power electronics, such as a battery or number of batteries, that give off non-negligible thermal energy (heat). The heat given off by the power electronics can cause a number of problems, such as reduced efficiency and/or damage to the power electronics, failure of the power electronics, and an increased risk of fire.

When sufficient heat has left interior compartment 30, paraffin pellet 42, acting as an actuator, will decrease in temperature. The decrease in temperature will change paraffin pellet 42 from a liquid to a solid, causing paraffin pellet 42 to decrease in volume. The decrease in volume of paraffin pellet 42 allows piston 40 to move and make available more volume within reservoir 24 for liquid 36 and less volume for gas 32. When this occurs, liquid 36 will flow from channel 22 into reservoir 24 and gas 32 will flow from reservoir 24 through vent tube 44 into channel 22, resulting in more gas 32 being present within channel 22 and a decrease in the thermal conductivity of channel 22.

The non-conducting mode, as seen in FIG. 1A, occurs when paraffin pellet 42 is in a solid state (the temperature is below the melting point of paraffin). When paraffin pellet 42 is in a solid state, piston 40 is located such that reservoir 24 is substantially filled by liquid 36 and channel 22 is substantially filled by gas 32. Such a configuration causes channel 22 to have a lower thermal conductivity than if liquid 36 was present within channel 22 (and act more as an insulator than if liquid 36 was present within channel 22). This may be desirable when the components in compartment interior 30, such as batteries, are not in operation or are just beginning operation.

Batteries, and other power electronics, generally provide lower performance in a low temperature environment. The power delivered by a battery in a low temperature environment may be less than required to, for example, start an engine. A sudden high power operation of power electronics from a low temperature environment may exacerbate temperature induced differential thermal expansion and cause degradation and/or damage of a component. To overcome these issues, a blanket heater or another heat generating device may be positioned adjacent to the power electronics to warm the power electronics to operating temperature. In this mode, it would be advantageous to minimize thermal conduction around compartment interior 30 to increase efficiency of the blanket heater, as well as longevity of the components in compartment interior 30.

Control assembly 18 of FIGS. 1A and 1B is a passive system that does not need input from a control device, but rather adjusts the position of piston 40 depending on the temperature in compartment interior 30 through the use of the thermally expansive and contractive paraffin pellet 42. The relatively simple design with minimal moving parts and input devices reduces the risk of malfunction and the possibility of the assembly breaking down while providing a system that can better control the temperature in compartment interior 30 to better protect the power electronics and increase efficiency. Devices other than paraffin pellet 42 may be utilized as an actuator to control the position of piston 40. Some of these devices (but not all) are discussed in regards to FIGS. 2, 3, and 4 below.

FIG. 2 is a schematic of the assembly of FIG. 1B showing a snap disk actuator. Similar to the embodiment of FIGS. 1A and 1B, control assembly 118 may include compartment 120, channel 122, and reservoir 124. Compartment 120 includes sides 126, double wall 128 (which includes exterior wall 128 a and interior wall 128 b), and compartment interior 130. Channel 122 includes gas 132 and fins 134 in the non-conducting mode, and gas 132, fins 134, and liquid 136 in the conducting mode. Reservoir 124 includes liquid 136 and drive 138 in the non-conducting mode, and gas 132, liquid 136, and drive 138 in the conducting mode. Control assembly 118 may also include vent tube 144.

Drive 38 of FIG. 2 includes piston 140, snap disk actuator 142, line 146, and temperature sensor 148. Snap disk actuator 142 is located within reservoir 124 and positioned such that piston 140 moves in response to the movement of snap disk actuator 142. Snap disk actuator 142 positions piston 140 depending on the temperature of compartment interior 130, which is measured by temperature sensor 148 and communicated by line 146 to snap disk actuator 142, which runs between snap disk actuator 142 and temperature sensor 148. Line 146 may be a high thermal conductivity path such as copper for a relatively short distance or may be a heat pipe for other than a short distance. Temperature sensor 148 for a conduction path or a heat pipe may be an enlarged end to increase thermal communication between compartment interior 130 and the conduction path or heat pipe. Temperature sensor 148 may be positioned anywhere throughout compartment interior 130, including directly adjacent to the power electronics or along one of sides 126. The placement of temperature sensor 148 depends on the configuration of the power electronics within compartment interior 130 and the desired minimum and maximum allowable temperatures within compartment interior 130, for temperature sensor 148 will have a higher temperature reading the closer it is to the heat source (i.e., the power electronics).

Snap disk actuator 142 is in mechanical communication with piston 140 and is configured to extend longitudinally along snap disk actuator 142 when prompted to move piston 140 and push liquid 136 into channel 122 to increase the thermal conductivity of control assembly 118. Snap disk actuator 142 is also configured to retract longitudinally when prompted to move piston 140 and allow gas 132 to flow into channel 122 to decrease the thermal conductivity of control assembly 118. Snap disk actuator 142 may also allow for other positions of piston 140 depending on the temperature of compartment interior 130 so that channel 122 is partially filled with gas 132 and liquid 136. Snap disk actuator 142 can be made from various materials known in the art. Other similar configurations may be used as an actuator in place of snap disk actuator 142, such as a bimetal actuator.

FIG. 3 is a schematic of the assembly of FIG. 1B showing a fluid expansion actuator. Similar to the embodiment of FIGS. 1A and 1B, control assembly 218 may include compartment 220, channel 222, and reservoir 224. Compartment 220 includes sides 226, double wall 228 (which includes exterior wall 228 a and interior wall 228 b), and compartment interior 230. Channel 222 includes gas 232 in the non-conducting mode, and gas 232 and liquid 236 in the conducting mode. Optionally, channel 222 may include fins as shown in FIGS. 1A, 1B, and 2. Reservoir 224 includes liquid 236 and drive 238 in the non-conducting mode, and gas 232, liquid 236, and drive 238 in the conducting mode. Control assembly 218 may also include vent tube 244.

Drive 238 of FIG. 3 includes piston 240, fluid expansion actuator 242, capillary line 246, sense bulb 248, and return spring 250. Fluid expansion actuator 242 is located within reservoir 224 and is positioned such that piston 240 moves in response to the movement of fluid expansion actuator 242. Fluid expansion actuator 242 positions piston 240 depending on the temperature of compartment interior 230, which is measured by sense bulb 248 and fluidically communicated to fluid expansion actuator 242 by capillary line 246, which runs between fluid expansion actuator 242 and sense bulb 248. Sense bulb 248 may be positioned anywhere throughout compartment interior 230, including directly adjacent to the power electronics or along one of sides 226. The placement of sense bulb 248 depends on the configuration of the power electronics within compartment interior 230 and the desired minimum and maximum allowable temperatures within compartment interior 230, for sense bulb 248 will have a higher temperature reading the closer it is to the heat source (i.e., the power electronics).

Sense bulb 248 contains a fluid that expands significantly and predictably with rising temperature. As the temperature within sense bulb 248 rises, the fluid flows through capillary line 246 into fluid expansion actuator 242 and pressure builds up within fluid expansion actuator 242, causing piston 240 to move and push liquid 236 into channel 222 and increase the thermal conductivity of control assembly 218. Piston 240 may be hermetically sealed with a bellows to prevent leakage past piston 240 into reservoir 224. Movement of piston 240 caused by fluid expansion actuator 242 may be proportional to the temperature of sense bulb 248, so channel 222 may be partially filled with gas 232 and liquid 236 to vary conductivity of control assembly 218. Opposing fluid expansion actuator 242 may be return spring 250, which can be located within reservoir 224. Return spring 250 is configured to push piston 240 when the pressure within fluid expansion actuator 242 decreases, allowing gas 232 to flow into channel 222 and liquid 236 to flow into reservoir 224, which causes the thermal conductivity of channel 222 to decrease.

FIG. 4 is a schematic of the assembly of FIG. 1B showing a solenoid actuator. Similar to the embodiment of FIGS. 1A and 1B, control assembly 318 may include compartment 320, channel 322, and reservoir 324. Compartment 320 includes sides 326, double wall 328 (which includes exterior wall 328 a and interior wall 328 b), compartment interior 230, and optionally electrical line 346. Channel 322 includes gas 332 in the non-conducting mode, and gas 332 and liquid 336 in the conducting mode. Optionally, channel 322 may include fins as shown in FIGS. 1A, 1B, and 2. Reservoir 324 includes liquid 336 and drive 338 in the non-conducting mode, and gas 332, liquid 336, and drive 338 in the conducting mode. Control assembly 318 may also include vent tube 344.

Drive 338 of FIG. 4 includes piston 340, solenoid actuator 342, electrical line 346, temperature switch 348, return spring 350, and power source 352. Solenoid 342 is located within reservoir 324 and is positioned such that piston 340 moves in response to the movement of solenoid actuator 342. Solenoid actuator 342 positions piston 340 depending on the temperature of compartment interior 330, which is determined by temperature switch 348 and communicated to solenoid actuator 342 by electrical line 346, which runs between solenoid actuator 342 and temperature switch 348.

Temperature switch 348 may be positioned anywhere throughout compartment interior 330, including directly adjacent to the power electronics or along one of sides 326. The placement of temperature switch 348 depends on the configuration of the power electronics within compartment interior 330 and the desired minimum and maximum allowable temperatures within compartment interior 330, for temperature switch 348 will have a higher temperature reading the closer it is to the heat source (i.e., the power electronics). Temperature switch 348 closes on increasing temperature to transmit electric power from power source 352 to solenoid actuator 342, which causes piston 340 to move toward solenoid actuator 342 and push liquid 336 into channel 322 (increasing thermal conductivity of control assembly 318). Decreasing temperature around temperature switch 348 removes power, causing solenoid actuator 342 to relax and allowing return spring 350 to push piston 340. This allows gas 332 to flow into channel 322 and liquid 36 to flow into reservoir 324 to decrease the thermal conductivity of control assembly 318.

Temperature switch 348 could have significant hysteresis to reduce cycling operation, or could be replaced by a sensor and electronic control for solenoid actuator 342. Also, solenoid actuator 342 could be replaced by an electromechanical actuator. Other configurations may be used as an actuator in a passive system. FIGS. 5A and 5B show the temperature control assembly utilizing an active system.

FIG. 5A is a schematic of a fluid based thermal conductivity control assembly showing an alternate embodiment in a non-conducting mode, while FIG. 5B is a schematic of the assembly of FIG. 5A in a conducting mode. Control assembly 418 may include compartment 420, channel 422, and reservoir 424. Compartment 420 includes sides 426, double wall 428 (which includes exterior wall 428 a and interior wall 428 b), and compartment interior 430. Channel 422 includes gas 432, fins 434, and separator 456 in the non-conducting mode, and liquid 436, fins 434, and separator 456 in the conducting mode. Reservoir 424 includes liquid 436, pump 454, and separator 456 in the non-conducting mode, and gas 432, liquid 436, pump 454, and separator 456 in the conducting mode. Control assembly 418 may also include line 446 and temperature sensor 448.

The configuration of control assembly 418 is very similar to control assembly 18 of FIGS. 1A and 1B, including compartment 420, double wall 428, and reservoir 424. Between exterior wall 428 a and interior wall 428 b is channel 422, which may include separator 456. Separator 456 divides channel 422 into two gaps: an ascending gap adjacent to exterior wall 428 a and a descending gap adjacent to interior wall 428 b. Separator 456 does not extend fully to the top of channel 422 so as to allow liquid 436 to flow from the ascending gap of channel 422 to the descending gap of channel 422. While fins 434 are shown adjacent to the inner surface of double wall 428, fins 434 may also be present on separator 456 or not included within channel 422 altogether. The ascending gap of channel 422 created by separator 456 encloses flow of liquid 436 into channel 422 from reservoir 424 while the descending gap of channel 422 created by separator 456 encloses flow of liquid 436 out of channel 422 back into reservoir 424.

Reservoir 424 is connected to channel 422 in a similar fashion as in FIGS. 1A and 1B. Within reservoir 424 is also separator 456, which extends from channel 422 into reservoir 424 and separates the flow path of liquid 436 into channel 422 and from channel 422 into reservoir 424. Separator 456 may be made from a material exhibiting high thermal conductivity, including the same material as double wall 428. Separator 456 does not extend fully through reservoir 424, but rather is configured to allow for a continuous flow path of liquid 436 through channel 422 and reservoir 424 (through the ascending gap and descending gap). Within reservoir 424 is pump 454, which is attached to temperature sensor 448 (located near or within interior compartment 430) by line 446. Pump 454 sits within liquid 436 in reservoir 424 and can be provided with power through various means known in the art.

In the non-conducting mode, as shown in FIG. 5A, pump 454 is not in operation and gas 432 is present within channel 422 while liquid 436 is only present within reservoir 424. Pump 454 will not be in operation when temperature sensor 448 indicates that compartment interior 430 is at or below a desired temperature. Because gas 432 is a substance with low conductivity, when only gas 432 is present within channel 422 control assembly 418 is not conductive. As with other embodiments in this disclosure, a non-conductive assembly may be desirable when the temperature in compartment interior 430 needs to be maintained or increased.

In the conducting mode, as shown in FIG. 5B, liquid 436 is present within channel 422. When liquid 436 is present within channel 422, heat can flow from compartment interior 430 through double wall 428, channel 422, liquid 436, and separator 456 out of the system to the exterior of compartment 420. Located adjacent to exterior wall 428 a may be a heat sink or other device able to accept thermal energy from control assembly 418.

Liquid 436 flows into channel 422 (into the ascending gap and out of the descending gap) through the use of pump 454, which is located within reservoir 424 and operates in response to temperature sensor 448 located near or in compartment interior 430. Pump 454 pushes liquid 436 from reservoir 424 into the ascending gap of channel 436. Liquid 436 then flows around the end of separator 456 and into the descending gap of channel 422. Liquid 436 then flows out of the descending gap of channel 422 into reservoir 424, where liquid 436 encounters pump 456 and repeats the flow cycle. The flow of liquid 436 is sufficient to bridge channel 422 and allow heat to be conducted out of compartment interior 430.

Temperature sensor 448 can be various apparatus, such as a sensor that controls the speed of pump 454 proportionate to the temperature of compartment interior 430 or an on-off switch that controls power to pump 454. The use of pump 454, along with temperature sensor 448, allows better control of the conductivity of control assembly 418 by varying the amount of liquid 436 flowing through channel 422. This better control increases the efficiency of control assembly 418 by only using as much power to run pump 454 to move liquid 436 as is needed to bring the temperature in compartment interior 430 to the desired level. Control assembly 418, like other embodiments in this disclosure, is also less complex than systems in the prior art, making control assembly 418 more reliable.

Discussion of Possible Embodiments

The following are non-exclusive descriptions of possible embodiments of the present invention.

A temperature control system may include a compartment having at least one side with low thermal conductivity and a side with a double wall, the side with the double wall having an interior wall adjacent to the interior of the compartment and an exterior wall, the interior wall and the exterior wall having high thermal conductivity and forming a channel therebetween; a reservoir connected to the channel; and a drive contained within the reservoir, wherein the drive is responsive to a temperature within the compartment to transfer a liquid with high thermal conductivity from the reservoir into the channel to increase thermal conductivity between the interior of the compartment and the exterior of the compartment and allows a gas with low thermal conductivity to be present within the channel when the channel does not contain the liquid to decrease thermal conductivity between the interior of the compartment and the exterior of the compartment.

The temperature control system of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations, and/or additional component.

The drive includes a piston and an actuator coupled to the piston, the actuator configured to move the piston to transfer the liquid or the gas into the channel.

The actuator includes a thermally activated bimetal actuator or a snap disk actuator in thermal communication with the compartment so as to move the piston in response to the temperature of the compartment.

The actuator includes a paraffin pellet in thermal communication with the compartment, the paraffin pellet configured to expand upon increase in temperature and contract upon decrease in temperature, the paraffin pellet configured so that the piston causes the liquid to be transferred into the channel when the paraffin pellet expands and causes the gas to be transferred into the channel when the paraffin pellet contracts.

The actuator includes a solenoid connected to a temperature sensor within the compartment so as to move the piston in response to the temperature of the compartment.

The actuator includes a fluid expansion actuator that communicates with the compartment through a temperature sense bulb so as to move the piston in response to the temperature of the compartment.

A vent tube that connects an upper part of the channel to a part of the reservoir containing only the gas.

The interior wall or the exterior wall includes at least one fin that protrudes into the channel.

A temperature sensor within the compartment that communicates with the drive.

The drive is a pump with a variable speed to transfer the liquid into the channel when increased thermal conductivity is desired.

A temperature sensor within the compartment that communicates with the pump to adjust the speed of the pump in response to the temperature of the compartment.

The channel is partially divided into at least two parts by a separator having high thermal conductivity.

A method for controlling the temperature of a compartment containing power electronics can include transferring a thermally conductive liquid from a reservoir into a channel that is adjacent to the compartment to increase the thermal conductivity between an interior of the compartment and an exterior of the compartment in response to a temperature within the compartment; and allowing a gas having low thermal conductivity to flow into the channel to decrease the thermal conductivity between the interior of the compartment and the exterior of the compartment in response to the temperature within the compartment.

The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations, and/or additional components.

The thermally conductive liquid is transferred from the reservoir into the channel by a drive that is responsive to the temperature within the compartment.

The drive includes a piston and an actuator located within the reservoir, the actuator attached at one end to the piston and at the other end to a wall of the reservoir, the actuator configured to move the piston to transfer the liquid into the channel when thermal conductivity is desired and the gas into the channel when thermal conductivity is not desired.

The actuator includes a paraffin pellet in thermal communication with the compartment, the paraffin pellet configured to expand upon increase in temperature and contract upon decrease in temperature, the paraffin pellet configured so that the piston causes the liquid to be transferred into the channel when the paraffin pellet expands and causes the gas to be transferred into the channel when the paraffin pellet contracts.

The actuator includes a bimetal or snap disk actuator in thermal communication with the compartment so as to move the displacer piston in response to the temperature of the compartment.

The actuator includes a fluid expansion actuator that communicates with the compartment through a temperature sense bulb so as to move the displacer piston in response to the temperature of the compartment.

The drive includes a pump with variable speed that transfers the liquid into the channel when in operation and the gas is within the channel when the pump is not in operation.

A wall of the channel includes at least one fin that protrudes into the channel.

Any relative terms or terms of degree used herein, such as “substantially,” “essentially,” “generally,” “approximately,” and the like, should be interpreted in accordance with and subject to any applicable definitions or limits expressly stated herein. In all instances, any relative terms or terms of degree used herein should be interpreted to broadly encompass any relevant disclosed embodiments as well as such ranges or variations as would be understood by a person of ordinary skill in the art in view of the entirety of the present disclosure, such as to encompass ordinary manufacturing tolerance variations, incidental alignment variations, alignment or shape variations induced by thermal, rotational or vibrational operational conditions, and the like.

While the invention has been described with reference to an exemplary embodiment(s), the invention will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed but that the invention will include all embodiments falling within the scope of the appended claims. 

1. A temperature control system, comprising: a compartment having an at least one side with low thermal conductivity and a side with a double wall, the side with the double wall having an interior wall adjacent to an interior of the compartment and an exterior wall, the interior wall and the exterior wall having high thermal conductivity and forming a channel therebetween; a reservoir connected to the channel; and a drive contained within the reservoir, wherein the drive is responsive to a temperature within the compartment to transfer a liquid with high thermal conductivity from the reservoir into the channel to increase thermal conductivity between the interior of the compartment and an exterior of the compartment and allows a gas with low thermal conductivity to be present within the channel when the channel does not contain the liquid to decrease thermal conductivity between the interior of the compartment and the exterior of the compartment.
 2. The temperature control system of claim 1, wherein the drive includes a piston and an actuator coupled to the piston, the actuator configured to move the piston to transfer the liquid or the gas into the channel.
 3. The temperature control system of claim 2, wherein the actuator includes a thermally activated bimetal actuator or a snap disk actuator in thermal communication with the compartment so as to move the piston in response to the temperature of the compartment.
 4. The temperature control system of claim 2, wherein the actuator includes a paraffin pellet in thermal communication with the compartment, the paraffin pellet configured to expand upon increase in temperature and contract upon decrease in temperature, the paraffin pellet configured so that the piston causes the liquid to be transferred into the channel when the paraffin pellet expands and causes the gas to be transferred into the channel when the paraffin pellet contracts.
 5. The temperature control system of claim 2, wherein the actuator includes a solenoid connected to a temperature sensor within the compartment so as to move the piston in response to the temperature of the compartment.
 6. The temperature control system of claim 2, wherein the actuator includes a fluid expansion actuator that communicates with the compartment through a temperature sense bulb so as to move the piston in response to the temperature of the compartment.
 7. The temperature control system of claim 1, further comprising: a vent tube that connects an upper part of the channel to a part of the reservoir containing only the gas.
 8. The temperature control system of claim 1, wherein the interior wall or the exterior wall includes at least one fin that protrudes into the channel.
 9. The temperature control system of claim 1, further comprising: a temperature sensor within the compartment that communicates with the drive.
 10. The temperature control system of claim 1, wherein the drive is a pump with a variable speed to transfer the liquid into the channel when increased thermal conductivity is desired.
 11. The temperature control system of claim 10, further comprising: a temperature sensor within the compartment that communicates with the pump to adjust the speed of the pump in response to the temperature of the compartment.
 12. The temperature control system of claim 10, wherein the channel is at least partially divided into at least two parts by a separator having high thermal conductivity.
 13. A method for controlling the temperature of a compartment containing power electronics, the method comprising: transferring a thermally conductive liquid from a reservoir into a channel that is adjacent to the compartment to increase the thermal conductivity between an interior of the compartment and an exterior of the compartment in response to a temperature within the compartment; and allowing a gas having low thermal conductivity to flow into the channel to decrease the thermal conductivity between the interior of the compartment and the exterior of the compartment in response to the temperature within the compartment.
 14. The method of claim 13, wherein the thermally conductive liquid is transferred from the reservoir into the channel by a drive that is responsive to the temperature within the compartment.
 15. The method of claim 14, wherein the drive includes a piston and an actuator located within the reservoir, the actuator attached at one end to the piston and at the other end to a wall of the reservoir, the actuator configured to move the piston to transfer the liquid into the channel when thermal conductivity is desired and the gas into the channel when thermal conductivity is not desired.
 16. The method of claim 15, wherein the actuator includes a paraffin pellet in thermal communication with the compartment, the paraffin pellet configured to expand upon increase in temperature and contract upon decrease in temperature, the paraffin pellet configured so that the piston causes the liquid to be transferred into the channel when the paraffin pellet expands and causes the gas to be transferred into the channel when the paraffin pellet contracts.
 17. The method of claim 15, wherein the actuator includes a bimetal or snap disk actuator in thermal communication with the compartment so as to move the displacer piston in response to the temperature of the compartment.
 18. The method of claim 15, wherein the actuator includes a fluid expansion actuator that communicates with the compartment through a temperature sense bulb so as to move the displacer piston in response to the temperature of the compartment.
 19. The method of claim 14, wherein the drive includes a pump with variable speed that transfers the liquid into the channel when in operation and the gas is within the channel when the pump is not in operation.
 20. The method of claim 13, wherein a wall of the channel includes at least one fin that protrudes into the channel. 